code: def backward_cpu(self, inputs, grad_outputs):
      return self._backward(inputs, grad_outputs)
  
file_path: chainer/chainer/functions/array/spatial_transformer_grid.py
imports: import numpy
  import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer import function
  from chainer.utils import argument
  from chainer.utils import type_check
label_desc: Use image node_id 6 for calling the SpatialTransformerGrid obj's underlying member method code with example usage: obj.backward_cpu(inputs, grad_outputs) and returns: self